cJSON

mirror of Dave's cJSON
git clone git://git.thc420.xyz/cJSON
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README.md (26139B)


      1 # cJSON
      2 
      3 Ultralightweight JSON parser in ANSI C.
      4 
      5 ## Table of contents
      6 * [License](#license)
      7 * [Usage](#usage)
      8   * [Welcome to cJSON](#welcome-to-cjson)
      9   * [Building](#building)
     10     * [Copying the source](#copying-the-source)
     11     * [CMake](#cmake)
     12     * [Makefile](#makefile)
     13   * [Including cJSON](#including-cjson)
     14   * [Data Structure](#data-structure)
     15   * [Working with the data structure](#working-with-the-data-structure)
     16     * [Basic types](#basic-types)
     17     * [Arrays](#arrays)
     18     * [Objects](#objects)
     19   * [Parsing JSON](#parsing-json)
     20   * [Printing JSON](#printing-json)
     21   * [Example](#example)
     22     * [Printing](#printing)
     23     * [Parsing](#parsing)
     24   * [Caveats](#caveats)
     25     * [Zero Character](#zero-character)
     26     * [Character Encoding](#character-encoding)
     27     * [C Standard](#c-standard)
     28     * [Floating Point Numbers](#floating-point-numbers)
     29     * [Deep Nesting Of Arrays And Objects](#deep-nesting-of-arrays-and-objects)
     30     * [Thread Safety](#thread-safety)
     31     * [Case Sensitivity](#case-sensitivity)
     32     * [Duplicate Object Members](#duplicate-object-members)
     33   * [Enjoy cJSON!](#enjoy-cjson)
     34 
     35 ## License
     36 
     37 MIT License
     38 
     39 >  Copyright (c) 2009-2017 Dave Gamble and cJSON contributors
     40 >
     41 >  Permission is hereby granted, free of charge, to any person obtaining a copy
     42 >  of this software and associated documentation files (the "Software"), to deal
     43 >  in the Software without restriction, including without limitation the rights
     44 >  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
     45 >  copies of the Software, and to permit persons to whom the Software is
     46 >  furnished to do so, subject to the following conditions:
     47 >
     48 >  The above copyright notice and this permission notice shall be included in
     49 >  all copies or substantial portions of the Software.
     50 >
     51 >  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
     52 >  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
     53 >  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
     54 >  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
     55 >  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
     56 >  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
     57 >  THE SOFTWARE.
     58 
     59 ## Usage
     60 
     61 ### Welcome to cJSON.
     62 
     63 cJSON aims to be the dumbest possible parser that you can get your job done with.
     64 It's a single file of C, and a single header file.
     65 
     66 JSON is described best here: http://www.json.org/
     67 It's like XML, but fat-free. You use it to move data around, store things, or just
     68 generally represent your program's state.
     69 
     70 As a library, cJSON exists to take away as much legwork as it can, but not get in your way.
     71 As a point of pragmatism (i.e. ignoring the truth), I'm going to say that you can use it
     72 in one of two modes: Auto and Manual. Let's have a quick run-through.
     73 
     74 I lifted some JSON from this page: http://www.json.org/fatfree.html
     75 That page inspired me to write cJSON, which is a parser that tries to share the same
     76 philosophy as JSON itself. Simple, dumb, out of the way.
     77 
     78 ### Building
     79 
     80 There are several ways to incorporate cJSON into your project.
     81 
     82 #### copying the source
     83 Because the entire library is only one C file and one header file, you can just copy `cJSON.h` and `cJSON.c` to your projects source and start using it.
     84 
     85 cJSON is written in ANSI C (C89) in order to support as many platforms and compilers as possible.
     86 
     87 #### CMake
     88 With CMake, cJSON supports a full blown build system. This way you get the most features. CMake with an equal or higher version than 2.8.5 is supported. With CMake it is recommended to do an out of tree build, meaning the compiled files are put in a directory separate from the source files. So in order to build cJSON with CMake on a Unix platform, make a `build` directory and run CMake inside it.
     89 
     90 ```
     91 mkdir build
     92 cd build
     93 cmake ..
     94 ```
     95 
     96 This will create a Makefile and a bunch of other files. You can then compile it:
     97 
     98 ```
     99 make
    100 ```
    101 
    102 And install it with `make install` if you want. By default it installs the headers `/usr/local/include/cjson` and the libraries to `/usr/local/lib`. It also installs files for pkg-config to make it easier to detect and use an existing installation of CMake. And it installs CMake config files, that can be used by other CMake based projects to discover the library.
    103 
    104 You can change the build process with a list of different options that you can pass to CMake. Turn them on with `On` and off with `Off`:
    105 * `-DENABLE_CJSON_TEST=On`: Enable building the tests. (on by default)
    106 * `-DENABLE_CJSON_UTILS=On`: Enable building cJSON_Utils. (off by default)
    107 * `-DENABLE_TARGET_EXPORT=On`: Enable the export of CMake targets. Turn off if it makes problems. (on by default)
    108 * `-DENABLE_CUSTOM_COMPILER_FLAGS=On`: Enable custom compiler flags (currently for Clang, GCC and MSVC). Turn off if it makes problems. (on by default)
    109 * `-DENABLE_VALGRIND=On`: Run tests with [valgrind](http://valgrind.org). (off by default)
    110 * `-DENABLE_SANITIZERS=On`: Compile cJSON with [AddressSanitizer](https://github.com/google/sanitizers/wiki/AddressSanitizer) and [UndefinedBehaviorSanitizer](https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html) enabled (if possible). (off by default)
    111 * `-DENABLE_SAFE_STACK`: Enable the [SafeStack](https://clang.llvm.org/docs/SafeStack.html) instrumentation pass. Currently only works with the Clang compiler. (off by default)
    112 * `-DBUILD_SHARED_LIBS=On`: Build the shared libraries. (on by default)
    113 * `-DBUILD_SHARED_AND_STATIC_LIBS=On`: Build both shared and static libraries. (off by default)
    114 * `-DCMAKE_INSTALL_PREFIX=/usr`: Set a prefix for the installation.
    115 * `-DENABLE_LOCALES=On`: Enable the usage of localeconv method. ( on by default )
    116 * `-DCJSON_OVERRIDE_BUILD_SHARED_LIBS=On`: Enable overriding the value of `BUILD_SHARED_LIBS` with `-DCJSON_BUILD_SHARED_LIBS`.
    117 
    118 If you are packaging cJSON for a distribution of Linux, you would probably take these steps for example:
    119 ```
    120 mkdir build
    121 cd build
    122 cmake .. -DENABLE_CJSON_UTILS=On -DENABLE_CJSON_TEST=Off -DCMAKE_INSTALL_PREFIX=/usr
    123 make
    124 make DESTDIR=$pkgdir install
    125 ```
    126 
    127 On Windows CMake is usually used to create a Visual Studio solution file by running it inside the Developer Command Prompt for Visual Studio, for exact steps follow the official documentation from CMake and Microsoft and use the online search engine of your choice. The descriptions of the the options above still generally apply, although not all of them work on Windows.
    128 
    129 #### Makefile
    130 **NOTE:** This Method is deprecated. Use CMake if at all possible. Makefile support is limited to fixing bugs.
    131 
    132 If you don't have CMake available, but still have GNU make. You can use the makefile to build cJSON:
    133 
    134 Run this command in the directory with the source code and it will automatically compile static and shared libraries and a little test program (not the full test suite).
    135 
    136 ```
    137 make all
    138 ```
    139 
    140 If you want, you can install the compiled library to your system using `make install`. By default it will install the headers in `/usr/local/include/cjson` and the libraries in `/usr/local/lib`. But you can change this behavior by setting the `PREFIX` and `DESTDIR` variables: `make PREFIX=/usr DESTDIR=temp install`.
    141 
    142 ### Including cJSON
    143 If you installed it via CMake or the Makefile, you can include cJSON like this:
    144 
    145 ```c
    146 #include <cjson/cJSON.h>
    147 ```
    148 
    149 ### Data Structure
    150 
    151 cJSON represents JSON data using the `cJSON` struct data type:
    152 
    153 ```c
    154 /* The cJSON structure: */
    155 typedef struct cJSON
    156 {
    157     struct cJSON *next;
    158     struct cJSON *prev;
    159     struct cJSON *child;
    160     int type;
    161     char *valuestring;
    162     /* writing to valueint is DEPRECATED, use cJSON_SetNumberValue instead */
    163     int valueint;
    164     double valuedouble;
    165     char *string;
    166 } cJSON;
    167 ```
    168 
    169 An item of this type represents a JSON value. The type is stored in `type` as a bit-flag (**this means that you cannot find out the type by just comparing the value of `type`**).
    170 
    171 To check the type of an item, use the corresponding `cJSON_Is...` function. It does a `NULL` check followed by a type check and returns a boolean value if the item is of this type.
    172 
    173 The type can be one of the following:
    174 * `cJSON_Invalid` (check with `cJSON_IsInvalid`): Represents an invalid item that doesn't contain any value. You automatically have this type if you set the item to all zero bytes.
    175 * `cJSON_False` (check with `cJSON_IsFalse`): Represents a `false` boolean value. You can also check for boolean values in general with `cJSON_IsBool`.
    176 * `cJSON_True` (check with `cJSON_IsTrue`): Represents a `true` boolean value. You can also check for boolean values in general with `cJSON_IsBool`.
    177 * `cJSON_NULL` (check with `cJSON_IsNull`): Represents a `null` value.
    178 * `cJSON_Number` (check with `cJSON_IsNumber`): Represents a number value. The value is stored as a double in `valuedouble` and also in `valueint`. If the number is outside of the range of an integer, `INT_MAX` or `INT_MIN` are used for `valueint`.
    179 * `cJSON_String` (check with `cJSON_IsString`): Represents a string value. It is stored in the form of a zero terminated string in `valuestring`.
    180 * `cJSON_Array` (check with `cJSON_IsArray`): Represent an array value. This is implemented by pointing `child` to a linked list of `cJSON` items that represent the values in the array. The elements are linked together using `next` and `prev`, where the first element has `prev == NULL` and the last element `next == NULL`.
    181 * `cJSON_Object` (check with `cJSON_IsObject`): Represents an object value. Objects are stored same way as an array, the only difference is that the items in the object store their keys in `string`.
    182 * `cJSON_Raw` (check with `cJSON_IsRaw`): Represents any kind of JSON that is stored as a zero terminated array of characters in `valuestring`. This can be used, for example, to avoid printing the same static JSON over and over again to save performance. cJSON will never create this type when parsing. Also note that cJSON doesn't check if it is valid JSON.
    183 
    184 Additionally there are the following two flags:
    185 * `cJSON_IsReference`: Specifies that the item that `child` points to and/or `valuestring` is not owned by this item, it is only a reference. So `cJSON_Delete` and other functions will only deallocate this item, not it's children/valuestring.
    186 * `cJSON_StringIsConst`: This means that `string` points to a constant string. This means that `cJSON_Delete` and other functions will not try to deallocate `string`.
    187 
    188 ### Working with the data structure
    189 
    190 For every value type there is a `cJSON_Create...` function that can be used to create an item of that type.
    191 All of these will allocate a `cJSON` struct that can later be deleted with `cJSON_Delete`.
    192 Note that you have to delete them at some point, otherwise you will get a memory leak.
    193 **Important**: If you have added an item to an array or an object already, you **mustn't** delete it with `cJSON_Delete`. Adding it to an array or object transfers its ownership so that when that array or object is deleted, it gets deleted as well.
    194 
    195 #### Basic types
    196 * **null** is created with `cJSON_CreateNull`
    197 * **booleans** are created with `cJSON_CreateTrue`, `cJSON_CreateFalse` or `cJSON_CreateBool`
    198 * **numbers** are created with `cJSON_CreateNumber`. This will set both `valuedouble` and `valueint`. If the number is outside of the range of an integer, `INT_MAX` or `INT_MIN` are used for `valueint`
    199 * **strings** are created with `cJSON_CreateString` (copies the string) or with `cJSON_CreateStringReference` (directly points to the string. This means that `valuestring` won't be deleted by `cJSON_Delete` and you are responsible for it's lifetime, useful for constants)
    200 
    201 #### Arrays
    202 
    203 You can create an empty array with `cJSON_CreateArray`. `cJSON_CreateArrayReference` can be used to create an array that doesn't "own" its content, so its content doesn't get deleted by `cJSON_Delete`.
    204 
    205 To add items to an array, use `cJSON_AddItemToArray` to append items to the end.
    206 Using `cJSON_AddItemReferenceToArray` an element can be added as a reference to another item, array or string. This means that `cJSON_Delete` will not delete that items `child` or `valuestring` properties, so no double frees are occuring if they are already used elsewhere.
    207 To insert items in the middle, use `cJSON_InsertItemInArray`. It will insert an item at the given 0 based index and shift all the existing items to the right.
    208 
    209 If you want to take an item out of an array at a given index and continue using it, use `cJSON_DetachItemFromArray`, it will return the detached item, so be sure to assign it to a pointer, otherwise you will have a memory leak.
    210 
    211 Deleting items is done with `cJSON_DeleteItemFromArray`. It works like `cJSON_DetachItemFromArray`, but deletes the detached item via `cJSON_Delete`.
    212 
    213 You can also replace an item in an array in place. Either with `cJSON_ReplaceItemInArray` using an index or with `cJSON_ReplaceItemViaPointer` given a pointer to an element. `cJSON_ReplaceItemViaPointer` will return `0` if it fails. What this does internally is to detach the old item, delete it and insert the new item in its place.
    214 
    215 To get the size of an array, use `cJSON_GetArraySize`. Use `cJSON_GetArrayItem` to get an element at a given index.
    216 
    217 Because an array is stored as a linked list, iterating it via index is inefficient (`O(n²)`), so you can iterate over an array using the `cJSON_ArrayForEach` macro in `O(n)` time complexity.
    218 
    219 #### Objects
    220 
    221 You can create an empty object with `cJSON_CreateObject`. `cJSON_CreateObjectReference` can be used to create an object that doesn't "own" its content, so its content doesn't get deleted by `cJSON_Delete`.
    222 
    223 To add items to an object, use `cJSON_AddItemToObject`. Use `cJSON_AddItemToObjectCS` to add an item to an object with a name that is a constant or reference (key of the item, `string` in the `cJSON` struct), so that it doesn't get freed by `cJSON_Delete`.
    224 Using `cJSON_AddItemReferenceToArray` an element can be added as a reference to another object, array or string. This means that `cJSON_Delete` will not delete that items `child` or `valuestring` properties, so no double frees are occuring if they are already used elsewhere.
    225 
    226 If you want to take an item out of an object, use `cJSON_DetachItemFromObjectCaseSensitive`, it will return the detached item, so be sure to assign it to a pointer, otherwise you will have a memory leak.
    227 
    228 Deleting items is done with `cJSON_DeleteItemFromObjectCaseSensitive`. It works like `cJSON_DetachItemFromObjectCaseSensitive` followed by `cJSON_Delete`.
    229 
    230 You can also replace an item in an object in place. Either with `cJSON_ReplaceItemInObjectCaseSensitive` using a key or with `cJSON_ReplaceItemViaPointer` given a pointer to an element. `cJSON_ReplaceItemViaPointer` will return `0` if it fails. What this does internally is to detach the old item, delete it and insert the new item in its place.
    231 
    232 To get the size of an object, you can use `cJSON_GetArraySize`, this works because internally objects are stored as arrays.
    233 
    234 If you want to access an item in an object, use `cJSON_GetObjectItemCaseSensitive`.
    235 
    236 To iterate over an object, you can use the `cJSON_ArrayForEach` macro the same way as for arrays.
    237 
    238 cJSON also provides convenient helper functions for quickly creating a new item and adding it to an object, like `cJSON_AddNullToObject`. They return a pointer to the new item or `NULL` if they failed.
    239 
    240 ### Parsing JSON
    241 
    242 Given some JSON in a zero terminated string, you can parse it with `cJSON_Parse`.
    243 
    244 ```c
    245 cJSON *json = cJSON_Parse(string);
    246 ```
    247 
    248 It will parse the JSON and allocate a tree of `cJSON` items that represents it. Once it returns, you are fully responsible for deallocating it after use with `cJSON_Delete`.
    249 
    250 The allocator used by `cJSON_Parse` is `malloc` and `free` by default but can be changed (globally) with `cJSON_InitHooks`.
    251 
    252 If an error occurs a pointer to the position of the error in the input string can be accessed using `cJSON_GetErrorPtr`. Note though that this can produce race conditions in multithreading scenarios, in that case it is better to use `cJSON_ParseWithOpts` with `return_parse_end`.
    253 By default, characters in the input string that follow the parsed JSON will not be considered as an error.
    254 
    255 If you want more options, use `cJSON_ParseWithOpts(const char *value, const char **return_parse_end, cJSON_bool require_null_terminated)`.
    256 `return_parse_end` returns a pointer to the end of the JSON in the input string or the position that an error occurs at (thereby replacing `cJSON_GetErrorPtr` in a thread safe way). `require_null_terminated`, if set to `1` will make it an error if the input string contains data after the JSON.
    257 
    258 ### Printing JSON
    259 
    260 Given a tree of `cJSON` items, you can print them as a string using `cJSON_Print`.
    261 
    262 ```c
    263 char *string = cJSON_Print(json);
    264 ```
    265 
    266 It will allocate a string and print a JSON representation of the tree into it. Once it returns, you are fully responsible for deallocating it after use with your allocator. (usually `free`, depends on what has been set with `cJSON_InitHooks`).
    267 
    268 `cJSON_Print` will print with whitespace for formatting. If you want to print without formatting, use `cJSON_PrintUnformatted`.
    269 
    270 If you have a rough idea of how big your resulting string will be, you can use `cJSON_PrintBuffered(const cJSON *item, int prebuffer, cJSON_bool fmt)`. `fmt` is a boolean to turn formatting with whitespace on and off. `prebuffer` specifies the first buffer size to use for printing. `cJSON_Print` currently uses 256 bytes for it's first buffer size. Once printing runs out of space, a new buffer is allocated and the old gets copied over before printing is continued.
    271 
    272 These dynamic buffer allocations can be completely avoided by using `cJSON_PrintPreallocated(cJSON *item, char *buffer, const int length, const cJSON_bool format)`. It takes a buffer to a pointer to print to and it's length. If the length is reached, printing will fail and it returns `0`. In case of success, `1` is returned. Note that you should provide 5 bytes more than is actually needed, because cJSON is not 100% accurate in estimating if the provided memory is enough.
    273 
    274 ### Example
    275 In this example we want to build and parse the following JSON:
    276 
    277 ```json
    278 {
    279     "name": "Awesome 4K",
    280     "resolutions": [
    281         {
    282             "width": 1280,
    283             "height": 720
    284         },
    285         {
    286             "width": 1920,
    287             "height": 1080
    288         },
    289         {
    290             "width": 3840,
    291             "height": 2160
    292         }
    293     ]
    294 }
    295 ```
    296 
    297 #### Printing
    298 Let's build the above JSON and print it to a string:
    299 ```c
    300 //create a monitor with a list of supported resolutions
    301 //NOTE: Returns a heap allocated string, you are required to free it after use.
    302 char* create_monitor(void)
    303 {
    304     const unsigned int resolution_numbers[3][2] = {
    305         {1280, 720},
    306         {1920, 1080},
    307         {3840, 2160}
    308     };
    309     char *string = NULL;
    310     cJSON *name = NULL;
    311     cJSON *resolutions = NULL;
    312     cJSON *resolution = NULL;
    313     cJSON *width = NULL;
    314     cJSON *height = NULL;
    315     size_t index = 0;
    316 
    317     cJSON *monitor = cJSON_CreateObject();
    318     if (monitor == NULL)
    319     {
    320         goto end;
    321     }
    322 
    323     name = cJSON_CreateString("Awesome 4K");
    324     if (name == NULL)
    325     {
    326         goto end;
    327     }
    328     /* after creation was successful, immediately add it to the monitor,
    329      * thereby transfering ownership of the pointer to it */
    330     cJSON_AddItemToObject(monitor, "name", name);
    331 
    332     resolutions = cJSON_CreateArray();
    333     if (resolutions == NULL)
    334     {
    335         goto end;
    336     }
    337     cJSON_AddItemToObject(monitor, "resolutions", resolutions);
    338 
    339     for (index = 0; index < (sizeof(resolution_numbers) / (2 * sizeof(int))); ++index)
    340     {
    341         resolution = cJSON_CreateObject();
    342         if (resolution == NULL)
    343         {
    344             goto end;
    345         }
    346         cJSON_AddItemToArray(resolutions, resolution);
    347 
    348         width = cJSON_CreateNumber(resolution_numbers[index][0]);
    349         if (width == NULL)
    350         {
    351             goto end;
    352         }
    353         cJSON_AddItemToObject(resolution, "width", width);
    354 
    355         height = cJSON_CreateNumber(resolution_numbers[index][1]);
    356         if (height == NULL)
    357         {
    358             goto end;
    359         }
    360         cJSON_AddItemToObject(resolution, "height", height);
    361     }
    362 
    363     string = cJSON_Print(monitor);
    364     if (string == NULL)
    365     {
    366         fprintf(stderr, "Failed to print monitor.\n");
    367     }
    368 
    369 end:
    370     cJSON_Delete(monitor);
    371     return string;
    372 }
    373 ```
    374 
    375 Alternatively we can use the `cJSON_Add...ToObject` helper functions to make our lifes a little easier:
    376 ```c
    377 //NOTE: Returns a heap allocated string, you are required to free it after use.
    378 char *create_monitor_with_helpers(void)
    379 {
    380     const unsigned int resolution_numbers[3][2] = {
    381         {1280, 720},
    382         {1920, 1080},
    383         {3840, 2160}
    384     };
    385     char *string = NULL;
    386     cJSON *resolutions = NULL;
    387     size_t index = 0;
    388 
    389     cJSON *monitor = cJSON_CreateObject();
    390 
    391     if (cJSON_AddStringToObject(monitor, "name", "Awesome 4K") == NULL)
    392     {
    393         goto end;
    394     }
    395 
    396     resolutions = cJSON_AddArrayToObject(monitor, "resolutions");
    397     if (resolutions == NULL)
    398     {
    399         goto end;
    400     }
    401 
    402     for (index = 0; index < (sizeof(resolution_numbers) / (2 * sizeof(int))); ++index)
    403     {
    404         cJSON *resolution = cJSON_CreateObject();
    405 
    406         if (cJSON_AddNumberToObject(resolution, "width", resolution_numbers[index][0]) == NULL)
    407         {
    408             goto end;
    409         }
    410 
    411         if(cJSON_AddNumberToObject(resolution, "height", resolution_numbers[index][1]) == NULL)
    412         {
    413             goto end;
    414         }
    415 
    416         cJSON_AddItemToArray(resolutions, resolution);
    417     }
    418 
    419     string = cJSON_Print(monitor);
    420     if (string == NULL) {
    421         fprintf(stderr, "Failed to print monitor.\n");
    422     }
    423 
    424 end:
    425     cJSON_Delete(monitor);
    426     return string;
    427 }
    428 ```
    429 
    430 #### Parsing
    431 In this example we will parse a JSON in the above format and check if the monitor supports a Full HD resolution while printing some diagnostic output:
    432 
    433 ```c
    434 /* return 1 if the monitor supports full hd, 0 otherwise */
    435 int supports_full_hd(const char * const monitor)
    436 {
    437     const cJSON *resolution = NULL;
    438     const cJSON *resolutions = NULL;
    439     const cJSON *name = NULL;
    440     int status = 0;
    441     cJSON *monitor_json = cJSON_Parse(monitor);
    442     if (monitor_json == NULL)
    443     {
    444         const char *error_ptr = cJSON_GetErrorPtr();
    445         if (error_ptr != NULL)
    446         {
    447             fprintf(stderr, "Error before: %s\n", error_ptr);
    448         }
    449         status = 0;
    450         goto end;
    451     }
    452 
    453     name = cJSON_GetObjectItemCaseSensitive(monitor_json, "name");
    454     if (cJSON_IsString(name) && (name->valuestring != NULL))
    455     {
    456         printf("Checking monitor \"%s\"\n", name->valuestring);
    457     }
    458 
    459     resolutions = cJSON_GetObjectItemCaseSensitive(monitor_json, "resolutions");
    460     cJSON_ArrayForEach(resolution, resolutions)
    461     {
    462         cJSON *width = cJSON_GetObjectItemCaseSensitive(resolution, "width");
    463         cJSON *height = cJSON_GetObjectItemCaseSensitive(resolution, "height");
    464 
    465         if (!cJSON_IsNumber(width) || !cJSON_IsNumber(height))
    466         {
    467             status = 0;
    468             goto end;
    469         }
    470 
    471         if ((width->valuedouble == 1920) && (height->valuedouble == 1080))
    472         {
    473             status = 1;
    474             goto end;
    475         }
    476     }
    477 
    478 end:
    479     cJSON_Delete(monitor_json);
    480     return status;
    481 }
    482 ```
    483 
    484 Note that there are no NULL checks except for the result of `cJSON_Parse` because `cJSON_GetObjectItemCaseSensitive` checks for `NULL` inputs already, so a `NULL` value is just propagated and `cJSON_IsNumber` and `cJSON_IsString` return `0` if the input is `NULL`.
    485 
    486 ### Caveats
    487 
    488 #### Zero Character
    489 
    490 cJSON doesn't support strings that contain the zero character `'\0'` or `\u0000`. This is impossible with the current API because strings are zero terminated.
    491 
    492 #### Character Encoding
    493 
    494 cJSON only supports UTF-8 encoded input. In most cases it doesn't reject invalid UTF-8 as input though, it just propagates it through as is. As long as the input doesn't contain invalid UTF-8, the output will always be valid UTF-8.
    495 
    496 #### C Standard
    497 
    498 cJSON is written in ANSI C (or C89, C90). If your compiler or C library doesn't follow this standard, correct behavior is not guaranteed.
    499 
    500 NOTE: ANSI C is not C++ therefore it shouldn't be compiled with a C++ compiler. You can compile it with a C compiler and link it with your C++ code however. Although compiling with a C++ compiler might work, correct behavior is not guaranteed.
    501 
    502 #### Floating Point Numbers
    503 
    504 cJSON does not officially support any `double` implementations other than IEEE754 double precision floating point numbers. It might still work with other implementations but bugs with these will be considered invalid.
    505 
    506 The maximum length of a floating point literal that cJSON supports is currently 63 characters.
    507 
    508 #### Deep Nesting Of Arrays And Objects
    509 
    510 cJSON doesn't support arrays and objects that are nested too deeply because this would result in a stack overflow. To prevent this cJSON limits the depth to `CJSON_NESTING_LIMIT` which is 1000 by default but can be changed at compile time.
    511 
    512 #### Thread Safety
    513 
    514 In general cJSON is **not thread safe**.
    515 
    516 However it is thread safe under the following conditions:
    517 * `cJSON_GetErrorPtr` is never used (the `return_parse_end` parameter of `cJSON_ParseWithOpts` can be used instead)
    518 * `cJSON_InitHooks` is only ever called before using cJSON in any threads.
    519 * `setlocale` is never called before all calls to cJSON functions have returned.
    520 
    521 #### Case Sensitivity
    522 
    523 When cJSON was originally created, it didn't follow the JSON standard and didn't make a distinction between uppercase and lowercase letters. If you want the correct, standard compliant, behavior, you need to use the `CaseSensitive` functions where available.
    524 
    525 #### Duplicate Object Members
    526 
    527 cJSON supports parsing and printing JSON that contains objects that have multiple members with the same name. `cJSON_GetObjectItemCaseSensitive` however will always only return the first one.
    528 
    529 # Enjoy cJSON!
    530 
    531 - Dave Gamble (original author)
    532 - Max Bruckner (current maintainer)
    533 - and the other [cJSON contributors](CONTRIBUTORS.md)